Parallel and perpendicular multilayer relaxation of Fe{310}

We report the results of a low-energy electron-diffraction analysis of the atomic structure of the {310} surface of body-centered-cubic iron. Damped relaxations from bulklike structure are found in the directions both parallel and perpendicular to the surface and extending four layers deep into the lattice. The surface structure is as follows: first interlayer spacing $d_{12}=0.76\mathrm{}\pm 0.03$ Å (bulk value is 0.906 Å), second interlayer spacing $d_{23}=1.02\mathrm{}\pm 0.03$ Å, third interlayer spacing $d_{34}=0.87\mathrm{}\pm 0.04$ Å, change of first-to-second layer registry shift $\Delta a_{12}=0.13\mathrm{}\pm 0.05$ Å, and change of second-to-third layer registry shift $\Delta a_{23}=0.03\mathrm{}\pm 0.05$ Å. Both changes of registry shifts are in the same direction, along a $〈310〉$ axis, and cause a decrease in the difference between nearest- and next-nearest-neighbor distances between atoms in adjacent layers.